Effects of oxytocin
and vasopressin on retrieval of passive avoidance response in
melatonin-treated and/or pinealectomized male rats Marlena
Juszczak, Edgar Appenrodt, Jan W. Guzek & Helmut Schwarzberg
Abstract
The role of the pineal gland and its hormone—melatonin—as
to the impact of vasopressin (VP) and/or oxytocin (OT) on the
regulation of behavior was studied, the passive avoidance task
being chosen as an experimental model. The results showed that
VP facilitated the avoidance latency during the first retention
trial; after pinealectomy, however, VP was ineffective in this
regard. Intraperitoneal application of OT was ineffective in
modifying the passive avoidance latency when compared with respective
saline-treated animals. Melatonin alone, when injected to sham operated
animals 30 min before behavioral experiment, did not affect
the passive avoidance response in SA- or OT-treated rats, but
blocked the VP-induced lengthening of the passive avoidance
latency in the first retention trial. In pinealectomized and
OT-treated animals the passive avoidance latency during the
second retention trial was severely diminished by melatonin
when compared to respective control. We conclude that: a) VP
needs a regulated pineal function for developing short-term
effects on the passive avoidance response and b) the effect
of OT on the avoidance latency in pinealectomized rats develops
after melatonin treatment as a long-term effect.
